Single-ply rubber membrane sheet materials are used for covering industrial and commercial flat or low slope roofs. The oldest and most effective means of securing single-ply rubber membranes to roof decks has been with solvent-based, contact-bond adhesives.
Other methods of membrane attachment include ballast stone and mechanical termination bars installed at lap areas under the outer edge of rubber sheets. Over a period of time, ballast stones damage rubber membranes. A ballast stone system has several other disadvantages. Over time, ballast stones also accumulate dirt and air-borne pollution that can further accelerate membrane damage. Also, ballast stones have been known to consolidate at certain areas on the roof leaving other areas bare. Furthermore, severe weather conditions can cause the ballast stones to become dangerous projectiles. In fact, housing codes have outlawed the use of ballast stones in some areas where severe weather, such as hurricanes, is likely to occur.
In a termination bar system, the termination bars secure the periphery of the rubber membrane and allow the membrane to repeatedly inflate upwardly when winds create a negative draft over the roof surface. The width of rubber roof membranes has recently increased from six feet to as much as twelve feet. Wider membrane sheets inflate more over a larger area thereby applying greater stress on the screws holding termination bars. With such increased wind uplift stress, failures in mechanically fastened roofs have likewise increased.
Fully adhered membrane systems use “solvent release” contact-bond adhesives that typically contain 80% volatile organic solvent. The solvents used are typically blends of toluene, xylene and hexane with small amounts of acetone. These solvents are extremely flammable and both hexane and toluene are toxic and carcinogenic with chronic exposure. Additionally, toluene and xylene polymerize in the atmosphere to form particulate air pollution.
Solvent release adhesives are difficult to spray effectively. In dry weather conditions, there is a risk of fire initiated by static electricity. In damp weather conditions atmospheric moisture is often caught up in a spray pattern resulting in water contamination known as “blush” at the bond interface. Such moisture trapped within the bond greatly diminishes bond strength.
Problems with spray application have forced the industry to rely on brush or roll coater application. These application methods have proven to be wasteful, less efficient and more labor intensive. Particularly problematic is the fact that conventional contact-bond adhesives must be applied to both opposing bond surfaces. When contact-bond adhesives are applied to both rubber membrane and roof deck surfaces they must be left open to the air for about fifteen minutes to allow the solvent to evaporate into the atmosphere before making a bond.
After the solvent is allowed to evaporate, the opposing coated surfaces are then carefully assembled, avoiding misalignment. An aggressive bond is formed with even light contact of one coated surface with the other. Misaligned bonds cause wrinkles or blisters that cannot be eliminated without damage to construction materials. The assembled sheets are then rolled or brushed, such as with push brooms, to set the bond over the entire membrane surface.
Because of the required application of adhesive to both surfaces, coverage is usually about fifty square feet of membrane to the gallon. More than a billion square feet of single-ply roofing is installed each year. The single-ply roofing industry annually applies more than 1,500,000 gallons of flammable, solvent-based contact adhesive. Eighty percent of this material is released into the atmosphere each year. This practice results in a chronic health risk for thousands roofing workers, a serious atmospheric insult, and a waste of petroleum resources.
Properly installed, fully adhered membrane systems still provide the most durable means of attachment for single-ply roofing. However, the costs associated with such systems, along with greater air-quality restrictions and worker safety concerns have pushed the industry toward more cost effective, safer and less environmentally contentious methods of attachment.
It is often assumed by roofing professionals, and others, that safe, environmentally compliant products are inherently more expensive and inferior in performance to solvent-based products. This invention shall demonstrate that solvent free products can be economically competitive and superior in performance to dangerous, flammable solvent-based materials.